The Math.log2()
function returns the base 2 logarithm of a number, that is
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Syntax
Math.log2(x)
Parameters
x
- A number.
Return value
The base 2 logarithm of the given number. If the number is negative, NaN
is returned.
Description
If the value of x
is less than 0, the return value is always NaN
.
Because log2()
is a static method of Math
, you always use it as Math.log2()
, rather than as a method of a Math
object you created (Math
is not a constructor).
This function is the equivalent of Math.log(x) / Math.log(2). For log2(e) use the constant Math.LOG2E
which is 1 / Math.LN2
.
Polyfill
This Polyfill emulates the Math.log2
function. Note that it returns imprecise values on some inputs (like 1 << 29), wrap into Math.round()
if working with bit masks.
if (!Math.log2) Math.log2 = function(x) { return Math.log(x) * Math.LOG2E; };
Examples
Using Math.log2()
Math.log2(3); // 1.584962500721156 Math.log2(2); // 1 Math.log2(1); // 0 Math.log2(0); // -Infinity Math.log2(-2); // NaN Math.log2(1024); // 10
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Math.log2' in that specification. |
Browser compatibility
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
log2 | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Firefox Android Full support 25 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support 3.0 | nodejs Full support 0.12 |
Legend
- Full support
- Full support
- No support
- No support